Calenders having two or more rollers disposed in a support column are known and are used for producing profile strips from elastomeric materials and for producing embossed films of thermoplastic materials. It is also known to provide at least one of such rollers with a roller shell which can be changed as desired.
Such a calender is disclosed in German Patent Specification No. 35 06 423. Such calender includes means permitting the change-over of the roller shell so that embossed films formed from thermoplastic plastics materials or profile strips formed from elastomeric materials can be produced. Such prior art calender comprises at least two rollers disposed in a support column and at least one of the rollers has a removable, profiled shell disposed around a roller core.
The roller shell serves to emboss individual profiles into the calendered products. In consequence, however, the roller shell needs to be changed every time it is desired to alter the goemetry of the profile. The operators of such calendering assemblies are therefore compelled to change the roller shell at relatively frequent intervals, particularly when small batches of products are being produced. This occurs, for example, when the assembly is being used for producing tires for specialist vehicles. It is, of course, desirable to keep the time taken for a change-over process to be effected as short as possible.
In an attempt to achieve this, it has been proposed, in the known assembly, to withdraw the bearing body of the roller having the shell to be changed from the calender support column and then to change-over the roller shell by withdrawing it through the calender support column, utilizing the free space produced by the removal of the bearing body.
For this purpose, the roller axle is made to protrude laterally beyond the calender support column. The protruding end of the axle is initially acted upon by means of a hydraulically actuated hold-down member so that the other end of the roller cannot drop once the bearing body has been removed. A centering cylinder is subsequently introduced into the end face of the roller core remote from the hold-down member and, by means of hydraulic piston and cylinder arrangements, the bearing body is drawn out of the calender support column over the end of the roller axle remote from the hold-down member. The hydraulically actuatable centering cylinder and the hydraulic piston and cylinder arrangements for the removal of the bearing body are mounted on a frame, which is horizontally pivotable about a pivot provided on the calender support column. A locking means is provided which is released after the bearing body and centering cylinder have been removed. The pivotable frame and the bearing body, are then pivoted away from the calender frame. The new roller shell is subsequently inserted through the aperture thus formed in the calender support column and the hinged frame is pivoted back into its original position and locked therein. After the centering cylinder has been introduced into the roller core, the bearing body is relocated on the roller pin and into the calender support column. The hold-down member for the other end of the axle roller is then raised.
However, while this arrangement for changing the roller shell has numerous advantages, it is also disadvantageous in that the removed bearing body cools during the change-over process and such cooling causes shrinkage. If the change-over operation takes a long time, there is the possibility that, when attempts are made to re-position the bearing body on the roller axle, the bearing body cannot be returned into its proper position, or can only be returned using additional, mechanical aids. This is a serious disadvantage because the operator of the system needs to effect the change-over as rapidly and as simply as possible.